Further aminized aminoalkylated celluloses by reacting with ethylenimine



Patented Oct. 20, 1853 UNITED STATES PATENT QFFICE FURTHER AMINIZEDANIINOALKYLATED CELLULOSES BY REACTING WITH ETH- YLENIMIN E AgricultureNo Drawing. Application May 11, 1951; Serial No. 225,906

(Granted under Title 35, U. S. Code (1952),

see. 266) 6 Claims.

This invention may be manufactured and used by or for the Government ofthe United States of America for governmental purposes throughout theworld without the payment to use of any royalty thereon.

This invention relates to cellulose derivatives which contain nitrogenin the form of amino groups and have ion-exchange properties which arenot substantially altered by each used and regeneration.

The invention particularly relates to a process for producing acellulose derivative which has a higher nitrogen content than thatobtainable by the 2-aminoethylsulfuric acid process, which nitrogen isin a form more firmly bound than the nitrogen in compositions containingthe same amount of nitrogen produced by the ethylenimine process.

One of the methods heretofore used to introduce amino groups involvesthe reaction of cellulose with an aminoalkylation agent such as ahaloethylamino hydrohalide or with Z-aminoethylsulfuric acid in thepresence of an alkali metal hydroxide. It has been well established thatsuch reactions produce aminoalkyl cellulose ethers. Such aminoalkylatedcelluloses have proven to be resistant to the action of acids and bases.However, when more than about 1% nitrogen is so introduced, the othersbecome more and more soluble in water, and the cellulosic fibrouscharacter is lost in that cellulosic fabrics so treated become stiff andboardy.

Another method heretofore used to introduce amino groups involves thereaction of cellulose with imines such as ethylenimine. Chemists havebeen unable to conclusively establish whether all of the iminepolymerizes upon the surfaces of the cellulosic fibers or whether someof it reacts to form aminoalkyl cellulose ethers. However, while up toabout 10% nitrogen has in some manner been combined with, or on,cellulose by such a treatment, very little of the nitrogen is firmlybound. Even when the nitrogen content is low, upon treatment withaqueous acids or bases, a substantial amount of the amino nitrogen islost.

The cellulosic derivatives containing amino groups and retaining acellulosic fibrous character have been found to exhibit particularlyvaluable anion-exchange properties. Hoffpauir and Guthrie reported, J.Biol. Chem. 178, 207-212, that in the preparation of oilseed proteins,Aminized cotton fabric was the most satisfactory anion-exchange materialfor the preparation of protein, since a higher pH could be obtained withit and the ash and phosphorus content of the preparation were lower thanthat obtained with either of the commercial anion-exchange resins. Theaminized cotton fabrics they used were pre pared by reacting cellulosewith Z-aminoethylsulfuric acid in the presence of sodium hydroxide bythe process of Patent 2,459,222 and contained 0.8% nitrogen.

We have found that while introducing additional amino groups by reactingan aminoalkylated cellulose with Z-aminoethylsulfuric acid in thepresence of an alkali metal hydroxide, or introducing additional aminogroups by reacting the composition produced by the reaction of cellulosewith ethylenimine with additional portions of ethylenimine, tends toproduce products which are soluble in water or easily decomposed byaqueous acids or bases; surprisingly, if an aminoalkylated cellulose isreacted with an alkylenimine, a totally diflerent type of product isproduced. The product produced by this latter method retains acellulosic fibrous character, and is more resistant to the action ofaqueous acids 3 and bases than is a product containing a like amount ofnitrogen produced by the ethylenimine method. It is therefore apparentthat reacting an aminoalkylated cellulose with ethylenimine produces adifferent substance than is produced by retreating cellulose one or moretimes with either an aminoalkylating agent such as Z-aminoethylsulfuricacid or with an alkylenimine such as ethylenimine.

While the invention is not to be construed as being dependent upon theoccurrence of a particular series of reactions, a possible explanationof the difference in the respective further aminized products is thefollowing. Aminoalkylated celluloses contain aminoalkyl groups attachedto the cellulosic nucleus by the relatively stable ether linkage. Whenthe ethylenimine is in contact with cellulose it is reasonable that thepolymerization of ethylenimine predominates, and the relatively solublepolyethyleneamine molecules form on the surfaces of the cellulosicmaterial. 0n the other hand, when the ethylenimine is in contact withaminoalkylated cellulose, it is reasonable that the reaction of theamino groups of the cellulose derivative with the ethyleniminepredominates, and the aminoethyl groups on the cellulosic nucleus areconverted to poly(ethyleneamino) aminoethyl groups. The occurrence ofthe above series of reactions would account for the fact that thereaction of aminoretains a substantially unchanged"ion-exchangecapacitythrough at least four use and regeneration cycles.

The further aminization processiof ,thisrinyenetion can be suitablyapplied to any form of an' aminoalkylated cellulose, for exampleto;am;ino.,- alkylated cotton, aminoalkylated,alpha-cellulose,aminoallgvlated viscose rayon, and-'the-like. PIB: ferred startingmaterials, comprise an aminoethylated cellulose containing from about0.5 to 1.8% nitrogen; and suchstarting -materialsare preferablyfurtheram-inized according toour-invention until they-contain from about2'to 5% nitrogen.

A" preferred-embodiment of the invention is in the-furtheraminizationofaminoalkylated cotton' cellulose in the form of yarn, particularlywhenthe yarn'is treated assuch or while-made up into a fabric. However, ingeneral, any oftheaminoalk-ylated celluleses can'be further-aminized bythe process of the invention'in theform of-raw-fibers, sliver; or in-adisintegratedor powdered form;

The reaction is preferably conductedfbvcontacting the aminoalkylatedcellulose with the vapors of 'ethylenimine at a temperature below thedecomposition temperature of the cellulosic material; However; in-thefurther: aminization of-certain aminoalkylated'celluloses; thealkylenimine can'be'dissolved'in a solventinert to theaminoalkylatedcellulose and" the reaction con-'- ducted in solution, forexample in a solution containing an imine such as N-cetyl ethyleniminein benzene, toluene; xylene, or other liquid hydrocarbons.

Ethylenimine is the preferredalk-ylenimine for employment intheprocessof; the invention; However, alkylenimines such as-2methylethylenimine,- 2,2-dimethylethylenimine and, in general; thehomologsof ethylenimine can suitably be employed.

The reaction'can beeonducted at any temperature fromaboutroom-temperature to-the-decomposition temperature of the cellulosic-material. However, temperatures of from ab'outfaf) -to-106 C.constitute-a preferred range of temperatures for employment in theprocess of the invention;

In conducting the process: inthe-preferred manner, i; e., incontacting-the aminoalkylated' cellulose withgthe vapors of theimine, itis-preferred to employ less than an equal: part of weight ofethylenimine. The use ofainounts-ofi from about 10: to" based upon.theweightof the: aminoalkylated cellulose have; been: found to bparticularly suitablewhere the. cellulosici material is placed in anevacuated; chamber-a which the imine is. allowed to. evaporate.

Where it is desired, to produce a; product; hav ing arelatively highnitrogen content, theyreace tion is -preferabl-yaccomplished in ,several,steps, contacting the aminoalkylated .cellulosewiththe preferred amountof imineimeach step.

The time. necessary to accomplish a given degree of furtheraminization,of course varies ,-wide- 1y. depending upon the temperature; and amount.

a ing atotal of 3. times.

of imine used. In general it has been found desirable to employtemperatures below about 100 C. and times of greater than about 6 hoursfor each treatment.

The following examples are presentedto illustrate in detail certainphases of the invention. However, as it is apparent that othermaterials, reactions, conditions.. and operative steps can be used, the:scope ofthe invention is defined by the appended claims, and theinvention is not to -be construed asgbeing limited to the particularsubstancesgorronerations recited in the examples.

Example 1 The fabric was now placed in a vacuum cham-.

ber heated to. C? After-the.- chamoer had-been evacuated, ethyleniminewas-introduced'dropwise into .the' chamber through an: addition tube. in

such awaythat it"vaporized 311.0808. The weight of ethylenimine used was16 percent of the weight of "the fabric- After i the. fabrichadareactecl for tlhreeidays.- with the ethylenimine vapor, it wasremoyed: and analyzed; It had an anion-exchange capacityof.1260:.milliequivalents per kg.

and anitrogen'contentzof-2i59 percent. After it hadbeen .used201166-1130 remove: hydrochloric acid from: dilute aqueous solution,being regenerated with dilute ammonium hydroxide solution. it had;

an anion-exchange capacity of .1206 and a nitrogencontentof;2.l4.upercent.. After it. hadbeen used .four. times toremovehydrochioric acid-fromdilute. aqueous-solutiomit had. ananion-exchange capacity-pf 1140::milliequivalentsper. leg. andianitrcgenpontent ofz 2;.2'l percent;. some of: the.

fabric; wasboiledxfor. 61. hours; with 2 percent sodium :hydroxidesolution. After this it had an anion-exchange- ;capacity'o-f :1560-.and-a nitrogen content 1 of 1.95 i percent.

In -Order to obtain: an. evf nz higher QJIiGIIrBLichange. capacity. thefabric wastrea-ted a second time=with ethylenimine- ,-by the. method 1described,

above. The ionrexchan e capacity-was now 2070 milliequivalents. per andtheni-trcgen content was-4.63 percent- After it had been usedonce.toremove hydrochloric acid from. dilute aqueous solution, beingregenerated with dilute ammonium hydroxide solution, it had ananion-exchange capacity of1830'and'a. nitrogen content of 3.63 percent;After d'cycles as an anion-exchanger its capacity was 1830milliequivalents per kg; and

its nitrogencontent was -S-J7'T-percent; After boiling-with sodiumhydroxide solution as previously described its anion excha-nge capacityM mill-iequivalents per Kg; and itsnitrogen content. was-2:79 percent;

. nitrogen content was 1.58 percent. After boiling.

with sodium hydroxide solution as previously described, the values-were. 900 and. 1.39 respectively,

Thisfabric was again put. throughthe part of.

theprocess. using,zraminoethylsulfu-ric. acid, ,make

It .now had an anion.-

exchange capacity of 1290 and a nitrogen content of 1.97 but was stiffand boardy and beginning to lose its fabric structure. After boilingwith sodium hydroxide solution as previously described, the values were1050 and 1.55 respec tively.

For comparative purposes some of the original untreated fabric was curedwith sodium hydroxide solution alone to give a control fabric and thiswas then processed with ethylenimine only at the 16 percent level aspreviously duscribed. The anion-exchange capacity was 770milliequivalents per kg. and the nitrogen content was 2.20 percent.After it had been used once to remove hydrochloric acid from diluteaqueous solution, being regenerated with dilute ammonium hydroxidesolution, it had an anion exchange capacity of 570 and a nitrogencontent of 1.09 percent. After 4 regeneration cycles the values were 520and 1.03 respectively. After boiling with sodium hydroxide solution asdescribed previously the values were 380 and 0.75 respectively. When thecontrol fabric was processed twice with ethylenimine alone at the 16percent level as previously described the values were 1310 and 3.38respectively, but these fell to 950 and 1.70 after one use and to 890and 1.65 after four regeneration cycles. After boiling with sodiumhydroxide solution as previously described the values were 680 and 1.26respectively.

A summary of the ion-exchange capacity of the materials made in theabove examples is given in the following table:

AESA represents Z-aminoethylsuliuric acid and Imine representsethylenimine.

Example 2 Coarse cotton bagging was put through the Z-aminoethylsulfuricacid process 5 times using a solution composed of 65 parts water, 25parts sodium hydroxide and 10 parts 2-aminoethylsulfuric acid. This wasto determine how high an anion-exchange capacity could be reached bythis process alone. The anion-exchange capacity was 1210 milliquivalentsper kg. and the nitrogen content was 1.71 percent. The fabric was,however, stiff and boardy and beginning to show signs of going intosolution. It was now processed with the vapor of ethylenimine at the 16percent level in a manner similar to that described in Example 1. Theanion-exchange capacity was now 2700 and the nitrogen content 5.00percent.

Having thus described our invention, we claim:

1. A process for the production of a cellulosic anion-exchange materialwhich comprises further aminizing an aminoethylated cellulose containingfrom about 0.5 to 1.8% nitrogen by reacting it with the vapors ofethylenimine until the reaction product contains from about 2 to 5%nitrogen.

2. The process of claim 1 in which the aminoethylated cotton cellulosefurther aminized is in the form of a fabric.

3. The process of claim 1 in which aminoethylated cellulose is furtheraminized by subjecting the aminoethylated cellulose to a series offurther amim'zation treatments using about 15%, by weight, ofethylenimine vapors and a temperature of about 70 C. in each treatment.

4. A process of producing an ion-exchange fabric which even after useand regeneration for at least four cycles has an ion-exchange capacityof at least about 1400 mini-equivalents, and which possesses cellulosicfibrous character comprising: reacting aminoethylated cotton fabriccontaining 0.5 to 1.8% nitrogen with ethylenimine until the fabriccontains from 2 to 5% nitrogen, the aminoethylated cotton being oneobtained by treating cotton fabric with aminoethylsulfuric acid andsodium hydroxide.

5. The process of claim 4 in which the ethylenimine is in the form of avapor.

6. The process of claim 4 in which the ethylenimine is dissolved in anorganic solvent.

GEORGE L. DRAKE, JR. JOHN D. GUTHRIE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,097,120 Fink et a1 Oct. 26, 1937 ,45 ,222 Guthrie Jan. 18,1949

4. A PROCESS OF PRODUCING AN ION-EXCHANGE FABRIC WHICH AFTER USE ANDREGENERATIONF OR AT LEAST FOUR CYCLES HAS AN ION-EXCHANGE CAPACITY OF ATLEAST ABOUT 1400 MILLI-EQUIVALENTS, AND WHICH POSSESSES CELLULOSICFIBROUS CHARACTER COMPRISING: REACTING AMINOETHYLATED COTTON FABRICCONTAINING 0.5 TO 1.8% NITROGEN WITH ETHYLENIMINE UNTIL THE FABRICCONTAINS FROM 2 TO 5% NITROGEN, THE AMINOETHYLATED COTTON BEING ONEOBTAINED BY TREATING COTTON FABRIC WITH AMINOETHYLSULFURIC ACID ANDSODIUM HYDROXIDE.